Wolfram Alpha
From DT Online
Wolfram Alpha is a computational knowledge engine, not a search engine. It is an engine for computing answers and providing knowledge.
It works by using its vast store of expert-level knowledge and algorithms automatically to answer questions, do analysis, and generate reports - e.g. in relation to: maths, engineering, science, materials, unit conversions, finance, music, geography, colours, dates & times, food & nutrition . . . and much more!